Device-to-Device (D2D) communication, which has recently emerged, refers to communication between devices via a direct link without intervention of a network entity such as a Base Station (BS).
A device supporting D2D service (e.g., a D2D device) acquires synchronization with a neighbor D2D device, detects or discovers the neighbor D2D device at a predetermined time in predetermined resources, and acquires device information about the discovered neighbor D2D device.
The device information may include identification information, interest information, and application program information about the neighbor D2D device. If the D2D device interacts with a BS, the D2D device discovers the neighbor D2D device at a time set by the BS in resources pre-allocated by the BS.
There are two types of D2D discovery schemes, stand-alone discovery (e.g., discovery without assistance from a network) and BS-assisted or network-assisted discovery. The stand-alone discovery scheme is advantageous in that a D2D device can acquire real-time information about a neighbor D2D device by transmitting a discovery signal around the D2D device.
According to the network-assisted discovery scheme, an assistant node such as a BS repeatedly transmits a discovery signal to neighbor D2D devices, thereby expanding discovery coverage and efficiently managing the energy of a D2D device. The assistant node transmits the discovery signal on behalf of the D2D device in an empty time interval (e.g., a non-signal transmission time interval) of a discovery period.
The stand-alone discovery scheme supports only limited coverage in view of hardware constraints imposed on a D2D device. In contrast, the network-assisted discovery scheme focuses only on the increase of energy efficiency and coverage expansion by simply repeating transmission of a discovery signal on behalf of a D2D device at an assistant node such as a BS in a communication network.
Various coverage areas of broadband networks such as cellular communication networks are interconnected around the world and thus a D2D device allowed to access a mobile communication network can perform discovery using a network entity (e.g., a BS) located in another region. Nonetheless, no discovery scheme using such a network entity has been specified.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.